The following images show prenatal findings in the double renal collecting system demonstrated on two cases diagnosed in our department.

Case 1

Images 1, 2: The images show dilated tortuous ureter within the fetal abdomen.

Images 3, 4: The image 3 compares the size of both fetal kidneys. The left affected kidney (calipers signed by the number 1) is larger and the dilated upper renal pelvis is clearly seen. The image 4 shows ureterocele within the lower part of the urinary bladder. The ureter leading to and forming the ureterocele comes from the dilated renal pelvis of the upper pole moiety of the affected left fetal kidney that can be seen on the image 3. The findings are part of the spectrum described by the Weigert-Meyer rule (see the drawing on the image 9).

Images 5, 6: The images show coronal scan of the fetal kidneys. The left kidney (the bottom one on the images) is larger and its dilated upper renal pelvis can be seen.

Case 2

Images 7, 8: The image 7 shows two renal pelvises of the right kidney (a small one and a dilated one signed by arrows). The image 8 shows ureterocele within the lower part of the urinary bladder. The ureter leading to and forming the ureterocele comes from the dilated renal pelvis of the upper pole moiety of the affected right fetal kidney shown on the image 7. The findings are part of the spectrum described by the Weigert-Meyer rule (see the drawing on the image 9).

Image 9: The image 9 shows a drawing explaining the Weigert - Meyer rule. The rule is applied to the duplex renal collecting system, when complete, duplicated ureters insert separately into the bladder.

According to the rule, the ureter of the upper pole moiety obstructs. The ectopic ureter and its orifice inserts medially and inferiorly to the ureter of the lower pole moiety, and frequently ends as a ureterocele (it can also insert into the urethra, vagina, etc). The ureter of the upper pole moiety of the affected kidney is often obstructed and the corresponding renal pelvis is dilated (hydronephrosis).

The ureter coming from the lower pole moiety of the kidney refluxes and inserts laterally and superiorly to the ectopic ureter of the upper pole moiety, and reflux at its level often causes pyelonephritis.